1. Field of the Invention
This invention relates to a tree pruning machine for cutting branches of a standing tree while climbing the tree and, more particularly, to a tree pruning machine having a body mounted on the standing tree and capable of vertically climbing the tree, and a rotary unit detachably mounted on the body for cutting branches projecting from the surface of the standing tree while the unit rotates around the body.
2. Description of the Relevant Literature
Tree pruning is necessary for cultivating high-grade timber without knots, for preventing damage by harmful insects or by snow, for accelerating growth of standing trees, for effectively utilizing a forest, or for pruning branches. Traditional branch pruning has been done manually. Since pruning is often done in mountains and other rugged terrain, the work has been very severe on labor, and a number of accidents have inevitably occurred. Additionally, the forest workers are often aged, and they are often incapable of withstanding the excessive demands on their ability, resulting in an overall decrease in the ability to meet present demands for branch pruning.
In view of the foregoing, automated tree pruning has been eagerly desired in the foresting industry. A variety of tree pruning machines have been proposed, but these tree pruning machines lack certain fundamental requirements. Particularly, a tree pruning machine must be capable of effectively climbing up and down a standing tree given the fact that trees gradually decrease in diameter from the root upwardly. To do this, a climbing mechanism must be capable of maintaining sufficient contact force with the surface of the tree despite the tree's varying diameter. Furthermore, the tree pruning machine must be stable as it climbs up and down the tree. If the pruning machine rocks while climbing up or down the tree, the cutting unit may cut into the bark of the tree, thereby damaging it, or the cutting unit may fail to cut the branch close enough to the tree trunk, thus allowing the root of the branch to remain as residual branches. These residual branches become head knots which decrease the commercial value of the timber. Additionally, the residual branches become obstacles to the pruning machine as it travels up and down the tree. Therefore, in order to satisfactorily prune the tree, the pruning machine must be capable of disposing the tree at the center of the machine regardless of changes in the diameter of the tree trunk.
The foregoing fundamental requirements for tree pruning machines are indispensable, and conventional tree pruning machines have not met such requirements, so an ideal tree pruning machine has not yet been invented.